import numpy as np
import matplotlib.pyplot as plt
import pandas as pd
import sys

x = np.linspace(0, 10, 11)
y1 = 10 + 3 * x
y2 = 5 * x
y3 = 20 - 2 * x
y4 = 3 * x**2 + 6 * x - 20

df = pd.DataFrame(np.c_[y1, y2, y3, y4],
                  columns=['y1', 'y2', 'y3', 'y4'])
print(df)
xcorr = df.corr()
print(type(xcorr))
print(xcorr)
